+Target *Tar::create_target(const list<Target *> &sources, const string &arg)
+{
+ if(!sources.front()->get_package())
+ throw invalid_argument("Tar::create_target");
+
+ TarBall *tarball = new TarBall(builder, *sources.front()->get_package(), arg);
+ for(Target *s: sources)
+ tarball->add_dependency(*s);